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Hatchbacks Honda Fit Honda Fit Real World MPG
2432 messages, Last post on Oct 29, 2009 at 4:50 AM
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Replying to: kipk (Mar 26, 2009 2:16 am) "If it was only 100 mpg going down, and 12 mpg up, the pencil average for the 2 would be 56 mpg." You're calculating your MPG wrong. If you drove 100 miles uphill at 12mpg that equals 8.3 gallons of gas used. If you drove 100 miles downhill at 100mpg that equals 1 gal used. So for the 200 miles driven you used 9.3 gal of gas and 200/9.3 = 21.5mpg average, not 56mpg average. Or best case and you use zero gallons on the 100 miles of downhill, then for the 200 miles you used 8.3 gallons, or 24.1mpg average over the 200 miles It's a common MPG calculation flaw. That if you drive 1/2 the miles at 20mpg and 1/2 the miles at 40mpg then your average MPG is 30...wrong because it's miles per gallon, not gallons per mile. Now if you use on gallon of gas at 20mpg and then drive the next gallon of gas at 40mpg, then your average MPG will be 30mpg because for the 1 gal at 20mpg you'll have driven 20 miles and then the next gallon you'll have driven 40 miles, which equals 60 miles using 2 gal which equals 30mpg. Just remember that MPG stands for Miles Per Gallons and not Gallons Per Mile. Bottom line is that if you're only getting 12mpg on the uphills even if you shut the car off on the downhills you're still only achieving 24mpg average, which is much worse then a steady 55mph on flat terrain. |
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Replying to: kipk (Mar 26, 2009 2:16 am) First law dictates that one many not create or destroy energy, only transfer it. Hill-climbing raises the car's potential energy that is converted back into kinetic energy upon descent. Second law says these processes must incur some energy loss to the outside world. For a car, wind resistance, friction, noise, heat from brakes, cooling system, exhaust are among these irreversible losses. (Hybrids achieve better mileage by capturing and storing energy that would have been dissipated by braking or rolling losses). A roller coaster illustrates the first law: speeds up going downhill as potential turns into kinetic energy (momentum), then slows again on climbing as kinetic energy is stored as potential. In cars, the efficiency of conversion of fuel to energy varies with load. Generally, lower power and steady-state (i.e., no change in power) yields higher efficiency. An engine running faster faces higher losses from larger volumes of exhaust, shorter power stroke duration, gearing loss in lower gears, greater heat transfer from combustion products to coolant and exhaust, etc. This translates into lower efficiency. It is possible but unlikely that an engine performs better at higher load than what is required for steady-state cruising. For that case, the power-then-coast method would improve mileage. But in general, given that no net energy is gained or lost from the inclines, wind and rolling resistance do not vary significantly from flat, the lower efficiency of the typical power plant on inclines will translate into lower mileage on hills.
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Hi Everyone: Just completed a road trip from our home on the San Francisco Peninsula to San Diego and back. The Sport Auto Fit worked very well as a freeway cruiser - even better than I thought it would. On the way down, with three of us in the car, we averaged 39.7 (computer) despite going 80-85 mph on Interstate 5. Driving around LA and the Palmdale desert, I was pleasantly surprised to get just under 42, despite climbing a few mountain passes up to about 4k'. I did not baby it. On the way home on highway 101 we got about 37. A beautiful time to drive through California. All green with wild flowers everywhere. Byron
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Replying to: wistlo (Mar 26, 2009 8:53 am) 
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Replying to: byron2 (Apr 08, 2009 9:06 pm)
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Replying to: xcentrick (Aug 26, 2008 8:21 pm)  63K miles, running very strong. Getting an avg of 33MPG driving ~120 miles/day, 80% freeway. Still have original tires, tread still legal, but intend to toss 65K miles. Just got my FIT shop manual from HelmInc today so I'll be changing out my timing belt about 70K miles. BTW, I also just got the shop manual for my refurbished '86 CRX HF (after 23 years) today I've owned since new, 310K miles, still runs as good as new, 43 MPG, 155# flat. rr
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Replying to: bobw3 (Apr 09, 2009 5:53 am) |
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Replying to: xcentrick (Apr 09, 2009 6:56 pm) I thought that the Fit used the timing chain, not a belt.
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Replying to: jacksan1 (Apr 10, 2009 11:36 am) Regards, Bubba 
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Replying to: Sylvia (Apr 22, 2006 8:32 pm)
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